Describe in detail what happened including the concern or potential issue, the environment (weather, terrain, fire behavior, etc), and the resulting health issue.

A mission was requested to install a portable repeater for the Fire. While Briefing the Communications Technician, it was decided to load the box with the repeater batteries/Antennae in the left side of the squirrel cheek. The com tech advised that he had loaded boxes like that before. After the helicopter landed at the pre- determined repeater site, the com tech opened the box (Fiberglass NIFC box). Upon opening the box the com tech smelled smoke and saw the remains of a burned envelope that was in the box. He also noted that the antennae in the box was still warm to the touch. It appeared that one of the VHF ground plane antenna laterals had contacted the battery terminals causing a short that heated the metal antenna and burned the envelope. This happened after loading and possibly during the flight to the repeater site. The com tech had checked the contents of the box the night before and everything seemed in order. The electrical short drained the battery, so another flight was made to replace the drained battery with a full one.

Immediate Action Taken

Reporting Individual : please describe actions you took to correct or mitigate the unsafe/unhealthful event.